EXPERIMENT STATION BULLETINS. 471 



was used. The ready capacity of lecithin to absorb gasoline-vapor, from 

 air containing it, is illustrated in the table. In connection with the 

 solubility of egg-white for gasoline, it must be remembered that even 

 egg-white is not pure albumen, but that it contains a mesh of extremely 

 fine membranes of keratin and a very small amount of fats, lecithin, and 

 cholesterin. The largest absorption of (3%) gasoline-vapor by 3 grms. 

 of egg-albumen was that given in Exp. No. 2 (0.7 c. c). A surprise 

 came in finding the comparative solubility of fresh egg-yolk for gasoline- 

 vapor as shown in the table. The results obtained in connection with 

 fresh and incubated egg-yolk will be referred to again under the next 

 heading. 



After these preliminary tests and other trials, lard was selected as 

 the fat and lecithin as the lipoid which seemed best adapted for the 

 purpose (according to the plan mentioned above) of being spread into 

 membranes to be used in determining the effect of gasoline-vapor upon 

 their permeability to oxygen of the air. However, a few tests were made 

 with membranes composed of a mixture of lard and lecithin, and also 

 with lanoline membranes. All these membranes were prepared, and 

 manipulated to obtain the results required by the plan, as follows: 



A very light India muslin was used for the sustaining fabric, and over 

 this the lecithin (or lard, etc.) was spread in a thin sheet entirely cover- 

 ing the fabric and filling its meshes to form essentially a lecithin (or 

 lard, etc.) membrane. In making use of such a lecithin membrane, for 

 example, it was placed as a cover over the mouth of a small preparation 

 dish (4 cm. in diameter), which had been almost but not quite filled with 

 concentrated lime-sulphur solution. The cover was then fastened down 

 ''lecithin tight" with a thin metal band, thus enclosing a small air space 

 above the lime-sulphur in the preparation dish. Great care Avas used 

 in order that the lime-sulphur might not wet the lecithin cover, and 

 the dish was floated up on mercury in the gas container of the apparatus, 

 Fig. III. In this position, the covered preparation dish Avas alloAved 

 to stand a fcAV hours. Then the mercury manometer '^m" Avas adjusted 

 level. The thermometer and barometer readings, the time and the read- 

 ing of the gas-burette '"a" Avere all recorded. After a certain definite 

 period all these readings Avere recorded again, the mercury-manometer 

 having been first leveled once more through adjusting the height of the 

 mercury column in the gas-burette ''a". In this manner, the rate of 

 volume-decrease of the air in the gas-container "c" was determined. The 

 decrease was due to a decrease in the amount of oxygen in the air of 

 the container holding the membraue-coA^ered dish of lime-sulphur solu- 

 tion. This Avas definitely. proven by determining the percentage of oxygen 

 in the air from samples taken from the container immediately before 

 the tests began and immediately after the last set of readings were 

 recorded— the volume of air used in the container during the test being 

 known. Since the conditions of the experiment have been outlined, it 

 Avill be clear that this rate of decrease in oxygen Ava.s the rate at Avliieh 

 oxygen was passing through the lecithin membrane — or whatever mem- 

 brane was used to cover the preparation dish. From the beginning of 

 the test, the lime-sulphur solution absorbed oxygen gradually and stead- 

 ily from the small air-space above it. Just as constantly, oxygen was 

 given off from the under side of the membrane (to the small air-space 

 above the lime-sulphur) and taken up or ahsorhed by the upper surface 

 of the membrane from the air of the container — the volume of Avhich was 



